Fix Exchange may still modify original requests

Author: nekohasekai

transport_tcp.go

@@ -79,7 +79,7 @@ func (t *TCPTransport) Exchange(ctx context.Context, message *dns.Msg) (*dns.Msg
 		return nil, err
 	}
 	defer conn.Close()
-	err = writeMessage(conn, message)
+	err = writeMessage(conn, 0, message)
 	if err != nil {
 		return nil, err
 	}
@@ -110,12 +110,13 @@ func readMessage(reader io.Reader) (*dns.Msg, error) {
 	return &message, err
 }
 
-func writeMessage(writer io.Writer, message *dns.Msg) error {
+func writeMessage(writer io.Writer, messageId uint16, message *dns.Msg) error {
 	requestLen := message.Len()
 	buffer := buf.NewSize(3 + requestLen)
 	defer buffer.Release()
 	common.Must(binary.Write(buffer, binary.BigEndian, uint16(requestLen)))
 	exMessage := *message
+	exMessage.Id = messageId
 	exMessage.Compress = true
 	rawMessage, err := exMessage.PackBuffer(buffer.FreeBytes())
 	if err != nil {

transport_tls.go

@@ -115,10 +115,8 @@ func (t *TLSTransport) Exchange(ctx context.Context, message *dns.Msg) (*dns.Msg
 }
 
 func (t *TLSTransport) exchange(message *dns.Msg, conn *tlsDNSConn) (*dns.Msg, error) {
-	messageId := message.Id
 	conn.queryId++
-	message.Id = conn.queryId
-	err := writeMessage(conn, message)
+	err := writeMessage(conn, conn.queryId, message)
 	if err != nil {
 		conn.Close()
 		return nil, E.Cause(err, "write request")
@@ -128,7 +126,6 @@ func (t *TLSTransport) exchange(message *dns.Msg, conn *tlsDNSConn) (*dns.Msg, e
 		conn.Close()
 		return nil, E.Cause(err, "read response")
 	}
-	response.Id = messageId
 	t.access.Lock()
 	t.connections.PushBack(conn)
 	t.access.Unlock()